Mozilla Foundation Security Advisory 2015-100

Arbitrary file manipulation by local user through Mozilla updater

Announced

September 22, 2015

Reporter

Holger Fuhrmannek

Impact

High

Products

Firefox, Firefox ESR, Thunderbird

Fixed in

Firefox 41

Firefox ESR 38.3

Thunderbird 38.3

Description

Security researcher Holger Fuhrmannek reported that when the
Mozilla updater is run, the updater can be manipulated to load the updated files from a
working directory under user control in concert with junctions. When the updates are run
by the Mozilla Maintenance Service on Windows, these malicious files can be run with
elevated privileges and be used to replace arbitrary files on the system. This could allow
for arbitrary code execution by a malicious user with local system access but does not
allow for exploitation by web content.

This issue is specific to Windows and does not affect Linux or OS X
systems.